The present invention relates to electrically conductive decorative materials, such as conductive decorative sheets or tiles, suitable as floor materials for use in factories handling ICs, LSIs and like electronic parts, laboratories or operating rooms, various clean rooms, etc.
In order to avoid electrostatic troubles, plastics or rubber floor materials filled with a large quantity of electrically conductive carbon black have heretofore been used in factories handling ICs, LSIs and like electronic parts, laboratories, operating rooms, etc. However, these floor materials, although producing an antistatic effect, have a black surface and are therefore low in decorative effect as interior finishing materials. To overcome this problem, JP-B No. 60-6429 proposes an interior finishing material comprising electrically non-conductive colored pellets and electrically conductive pellets. This material has a decorative effect and exhibits a considerable antistatic effect, whereas the conductive pellets used are black pellets incorporating conductive carbon black, giving a dark color to the material in its entirety. Further when this floor material is used in electronic part factories handling ICs, LSIs or the like, the material is subjected for example, to a voltage of at least 300 V to 10 KV as measured by the Honest Meter method, causing a voltage breakdown of electronic parts. The term, "voltage breakdown" refers to the phenomenon that electric charge stored in the human body, which can be viewed as a capacitor, flows out into an electronic part to break down the part. The voltage breakdown invariably occurs when the charge voltage is at least 100 V. To preclude this, the charge voltage is preferably no more than 50 V, more preferably not greater than 30 V. The known floor material nevertheless has the problem that the charge on the nonconductive pellets is not readily removable but induces a voltage breakdown. Further with the above floor finishing materials wherein conductive carbon black is used, fine particles of carbon black become suspended in the air owing to the wear of the surface to degrade the clean atmosphere of factories handling ELSIs, precision electronic parts or the like,laboratories or clean rooms.
An object of the present invention is to provide an electrically conductive decorative material having an excellent conductive properties along with a decorative effect and a light-colored appearance.
Another object of the present invention is to provide an electrically conductive decorative material free of the problem of dust and like particles.